Fishes and Amphibians Chapter 28
Section 28.1 Section 30.1 Summary – pages 793-802 What is a fish? • Fishes, like all vertebrates, are classified in the phylum Chordata. • Fishes belong to the subphylum Vertebrata.
Section 30.1 Summary – pages 793-802 What is a fish? • In addition to fishes, subphylum Vertebrata includes amphibians, reptiles, birds, and mammals.
Section 30.1 Summary – pages 793-802 What is a fish? • In vertebrates, the embryo’s notochord is replaced by a backbone in adult animals. • All vertebrates are bilaterally symmetrical, coelomates that have endoskeletons,( made of cartilage or bone) closed circulatory systems, nervous systems with complex brains and sense organs, and efficient respiratory systems. • * is a tough, flexible material
Fishes and Amphibians Section 1 Fishes Neural Crest • A neural crest is a group of cells that develop from the nerve cord in vertebrates. • Portions of the brain and skull, certain sense organs, and some nerve fibers are some of the structures that develop from the neural crest.
Key Characteristics of Modern Fishes Section 30.1 Summary – pages 793-802 • Despite the variation – all fish have Gills, single loop blood circulation, and a backbone. • 1.Fish breathe using gills • Fish have gills made up of feathery gill filaments that contain tiny blood vessels through which gases enter and leave the blood. Gill Filaments
Fishes breathe using gills Section 30.1 Summary – pages 793-802 • As a fish takes water in through its mouth, water passes over the gills and then out through gill slits at the side of the fish. • Gill cover= operculum Gill Filaments • Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments. In a countercurrent flow.(=blood flows in one direction and water in the opposite direction.) Capillary networks in filament Water Gill filaments Artery Vein Water
2. Single-loop blood circulation- • Blood is pumped from the heart to the capillaries in the gills. • From the gills, blood passes to the rest of the body and then returns to the Heart. • a.) Sinus Venous- collection chamber- reduces the resistance of blood flow into the heart. • b.) Atrium- delivers blood to ventricle • c.) Ventricle- forces blood to flow through the gills and eventually to the rest of the body. • d.) Conusarteriosus- smoothes the pulsations and adds still more force. • Lungfishes are an exception they have a double loop.
Section 30.1 Summary – pages 793-802 Fishes have two-chambered hearts Aorta Capillary network Gills Heart
5. Reproduction Section 30.1 Summary – pages 793-802 • Although the method may vary, all fishes reproduce sexually. • Fertilization and development is external in most fishes. • Eggs and sperm can be released directly into the water, or deposited in more protected areas, such as on floating aquatic plants. • A yolk sac within each egg contains nutrients the developing embryo will need for growth.
Section 30.1 Summary – pages 793-802 Fishes reproduce sexually • Most bony fishes have external fertilization and development. • This type of external reproduction in fishes and some other animals is called spawning. Salmon spawning
Section 30.1 Summary – pages 793-802 Fishes reproduce sexually • Cartilaginous fishes have internal fertilization. • Skates deposit fertilized eggs on the ocean floor. • Some female sharks and rays carry developing young inside their bodies. • A few species of sharks lay eggs. • During mating, the male uses two organs called claspers to insert sperm into the female.
Section 30.1 Summary – pages 793-802 Fishes reproduce sexually • In some bony fishes, such as guppies and mollies, fertilization and development is internal. • Most fishes that produce millions of eggs provide no care for their offspring after spawning. • Some fishes, such as the mouth-brooding cichlids, stay with their young after they hatch.
Section 30.1 Summary – pages 793-802 Most fishes have paired fins • Fishes in the classes Chondrichthyes and Osteichthyes have paired fins. • Fins are fan-shaped membranes that are used for balance, swimming, and steering.
3. Vertebral column (backbone) • made of either cartilage or bone • Surrounds the spinal cord • Brain is encased with the skull or cranium. 4. Kidneys- Nephrons- are tube-like units that regulate the body’s salt and water balance and remove metabolic wastes from the blood. Freshwater fish excrete large amounts of urine compared to marine fish due to osmosis and ion exchange. * to make up for the water they lose by osmosis, marine fish drink sea water & pump out excess ions out of their bodies.
Section 30.1 Summary – pages 793-802 Most fishes have paired fins • Fins are attached to and supported by the endoskeleton and are important in locomotion.
Section 30.1 Summary – pages 793-802 Most fishes have paired fins • The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying. Dorsal fins Pectoral fin Anal fin Caudal fin Pelvic fins
Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems • The lateral line system is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water. Lateral line Gelatin-like fluid Receptor cells Nerve
Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems • Fishes have eyes that allow them to see objects and contrasts between light and dark in the water as well. • Some fishes that live in areas of the ocean where there is no light may have reduced, almost nonfunctional eyes.
Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems • Some fishes also have an extremely sensitive sense of smell and can detect small amounts of chemicals in the water. • Sharks can follow a trail of blood through the water for several hundred meters.
Fishes and Amphibians Section 1 Scales • There are four types of fish scales. • Placoid scales -made of tooth like material and are rough and heavy (shark) • Ctenoid scales- tooth like a comb • Cycloid scales- made of bone and skin • Ganoid scales-made of enamel and bone
Section 30.1 Summary – pages 793-802 Jaws evolved in fishes Gill arches Gill slits Jawless, filter-feeding fish Jaws Skull Gill slits Gill arches Fish with jaws Beginning of jaw formation • The gill arches evolved to form the jaw!!
Section 30.1 Summary – pages 793-802 Jaws evolved in fishes Gillarches Gill slits Gill arches Gill slits Jaws Skull Jawless, filter-feeding fish Beginning of jaw formation Fish with jaws • Jaws also allowed early fishes to prey on a greater variety of organisms. • The advantage of jaws is that they enable an animal to grasp and crush its prey with great force
Section 30.1 Summary – pages 793-802 Jaws evolved in fishes • Sharks have up to 20 rows of teeth that are continually replaced. • Their teeth point backwards to prevent prey from escaping once caught.
Section 30.1 Summary – pages 793-802 Jaws evolved in fishes • Sharks are among the most streamlined of all fishes and are well adapted for life as predators.
Section 30.1 Summary – pages 793-802 Most fishes have bony skeletons • Bony fishes, a successful and widely distributed class, differ greatly in habitat, size, feeding behavior, and shape.
Section 30.1 Summary – pages 793-802 Classes of fishes Fishes Organisms Characteristics Class Jawless, cartilaginous skeleton, gills Myxini Hagfishes Jawless, cartilaginous skeleton, gills Lampreys Cephalaspidomorphi Jaws, cartilaginous skeleton, paired fins, gills, scales, internal fertilization Chondrichthyes Sharks, skates, rays Jaws, bony skeleton, paired fins, gills, scales, swim bladder Lobe-finned fishes, ray-finned fishes Osteichthyes
Section 30.1 Summary – pages 793-802 Bony fishes have separate vertebrae that provide flexibility • The evolution of a backbone composed of separate, hard segments called vertebrae was significant in providing the major support structure of the vertebrate skeleton. • Separate vertebrae provide great flexibility.
Section 30.1 Summary – pages 793-802 Bony fishes evolved swim bladders Swim bladder • A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder.
Section 30.1 Summary – pages 793-802 Bony fishes evolved swim bladders • Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus. • In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood.
Section 30.1 Summary – pages 793-802 A Bony Fish Lateral line system Swim bladder Kidney Scales Urinary bladder Reproductive organ Fins Stomach Intestine Liver Heart Gills
Section 28.2 Section 30.1 Summary – pages 793-802 Diversity of fishes • Fishes range in size from the tiny dwarf goby that is less than 1 cm long, to the huge whale shark that can reach a length of about 15 m—the length of two school buses. Whale shark
Section 30.1 Summary – pages 793-802 Agnathans are jawless fishes • Lampreys and hagfishes belong to the superclass Agnatha. Lamprey • The skeletons of agnathans, as well as of sharks and their relatives, are made of a tough, flexible material called cartilage. • Lampreys and Hagfish have a notochord in all stages of their life. (even adulthood)
Section 30.1 Summary – pages 793-802 Agnathans are jawless fishes • A hagfish has a toothed mouth and feeds on dead or dying fishes. • It can drill a hole into a fish and suck out the blood and insides. • Parasitic lampreys use their suckerlike mouths to attack other fishes. • They use their sharp teeth to scrape away the flesh and then suck out the prey’s blood.
Section 30.1 Summary – pages 793-802 Sharks and rays are cartilaginous fishes • Sharks, skates, and rays belong to the class Chondrichthyes. • These fishes, like agnathans, possess skeletons composed entirely of cartilage. • Sharks are perhaps the most well-known predators of the oceans.
Section 30.1 Summary – pages 793-802 Sharks and rays are cartilaginous fishes • Like sharks, most rays are predators and feed on or near the ocean floor. • Ras have flat bodies and broad pectoral fins on their sides.
Section 30.1 Summary – pages 793-802 Sharks and rays are cartilaginous fishes • By slowly flapping their toes up and down, rays can glide as they search for mollusks and crustaceans along the ocean floor.
Section 30.1 Summary – pages 793-802 Subclasses of bony fishes (see p. 831) • Scientists recognize two subclasses of bony fishes—the lobe-finned fishes, including lungfishes, and the ray-finned fishes. • The lobe-finned fishes are represented by seven living species: six species of lungfishes, which have both gills and lungs, and the coelacanth. • Each fin consists of a long, fleshy muscular lobe that is supported by a central core of bones. • A third group (now extinct) - Is the tetrapod
Section 30.1 Summary – pages 793-802 Subclasses of bony fishes • In the ray-finned fishes, such as catfish, perch, salmon, and cod, fins are fan-shaped membranes supported by stiff spines called rays. • Teleosts- have highly mobile fins • Very thin scales • Completely symmetrical tails • 95% of all ray finned fish are teleosts. Perch
Section 30.1 Summary – pages 793-802 Evolution of Fishes • Scientists have identified fossils of fishes that existed during the late Cambrian Period, 500 million years ago. • At this time, ostracoderms (OHS trah koh durmz), early jawless fishes, were the dominant vertebrates on Earth.
Section 30.1 Summary – pages 793-802 Origins of Fishes Heterostracah Anaspid Cephalaspid
Section 30.1 Summary – pages 793-802 Origins of Fishes • Bone provides a place for muscle attachment, which improves locomotion. • In ancestral fishes, bone that formed into plates provided protection as well.
Section 30.1 Summary – pages 793-802 Origins of Fishes • Scientists hypothesize that the jawless ostracoderms were the common ancestors of all fishes. • Modern cartilaginous and bony fishes evolved during the mid-Devonian Period. • Lobe-finned fishes, such as coelacanths (SEE luh kanths), are another ancient group, appearing in the fossil record about 395 million years ago.
Key Characteristics of Amphibians Section 30.2 Summary – pages 803-809 • Legs- most have 4, Caecilians have none. • Amphibians have thin, moist skin (cutaneous respiration) • Lungs- is an internal , baglike respiratory organ. • -In the larval form they have gills not lungs.
4. Double Loop circulation Section 30.2 Summary – pages 803-809 • Two large veins called pulmonary veins return oxygen rich blood from the lungs to the heart. • The evolution of the three-chambered heart in amphibians ensured that cells received the proper amount of oxygen. • Blood from both chambers then moves to the third chamber, (=ventricle) which pump oxygen-rich blood to body tissues and oxygen-poor blood back to the lungs and skin so it can pick up more oxygen.
5. Partially Divided Heart Section 30.2 Summary – pages 803-809 • In the three-chambered heart of amphibians, one chamber receives oxygen-rich blood from the lungs and skin, and another chamber receives oxygen-poor blood from the body tissues. (=atrium) divided into left and right sides. • A dividing wall known as the septum separates the atrium into a right and left. 6. Cutaneous Respiration- amphibians have thin, moist skin which they use to supplement their oxygen content.
Section 30.2 Summary – pages 803-809 Frogs and toads belong to the order Anura • Frogs and toads are amphibians with no tails. • Frogs have long hind legs and smooth, moist skin. Frog Toad
Section 30.2 Summary – pages 803-809 Frogs and toads belong to the order Anura • Toads have short legs and bumpy, dry skin. • Adult frogs and toads are predators that eat invertebrates, such as insects and worms.(=carnivorous) Frog Toad
Section 30.2 Summary – pages 803-809 • Because the skin of an amphibian must stay moist to exchange gases, most amphibians are limited to life on the water’s edge or other moist areas.